I am reading a speech by Michael Mann, the author of the now famous climate hockey stick, which has been criticized by statisticians and climatologists alike. In particular, I am fascinated by the claim that "there is a 95 to 99% certainty that 1998 was the hottest year in the last one thousand years."

Forgetting the problems with his analysis, and forgetting all the other evidence that we have that in the Medieval warm period, the earth was probably hotter than it was today, just look at that sentence on its face. Is there any other context where we would take a scientists near certainty about the value of a climate variable 500 years before man even started measuring it as anything but quackery? If there was a way to reasonably bet against the proposition that 1998 was the hottest year of the millennium, I would do so even as a 1:1 proposition, but would leap at the chance to take the bet at 20:1 or 100:1 odds, which is essentially what Mann is proposing when he says he is 95-99 percent certain.

Now, I often agree with most everything you say, but you're not well-founded here. There are proxies for temperature over time, just like there are ways to determine the age of bones and fossils. Would you describe a statement that "these primitive people lived in this area 10,000 years ago" as quackery?

Because they're using similar concepts - one measures carbon-14, the other (temperature proxies) looks at tree ring data and correlates it to current temperature data to extrapolate what happened in the past. That's not unreasonable, and, for that matter, that's the same technique that shows that the Medieval Warming Period occurred (although GW advocates claim that the MWP was a local event, or never occurred at all)

For what it's worth, I generally agree that yes, man-made CO2 is having some effect, but it's not nearly as dire as the anti-capitalists claim that it is. I am also expect that increased cloud cover predicted by climate models will provide a significant negative feedback to the warming cycle.

steep

jb,

You should do a little reading at climateaudit.org. I'm sure the discussion
there will help you understand why coyote says quackery. Especially any
discussion of the statistical methods used by dendro climatologists.

BTW, the evidence for MWP is historical (ie. settlements in Greenland,
Grapes in England, etc.) Recent tree-ring proxies seem to try to refute the history.